I've asked on other forums, but would like to ask here too. I have a new XC70 with about 500 miles on it so far. I plan to change to synthetic oil once the engine has been run enough for the valves to seat, etc. The question is how soon to do that? Recommendations on other forums have ranged from about 1,500 to 5,000 miles. In advance, thanks. This website is a great source of advice and information!